1. Field of the Invention
The present invention relates to a thermal treatment apparatus, a semiconductor device fabrication apparatus, a load-lock chamber of such a semiconductor device fabrication apparatus, and a method of fabricating a semiconductor device using such a thermal treatment apparatus or such a semiconductor device fabrication apparatus.
2. Description of the Prior Art
Recently, it has been of an important task in semiconductor fabrication technology to suppress the formation of a native oxide film. If a native oxide film is formed on a semiconductor substrate, then the leakage current of a semiconductor device that is fabricated is increased, the dielectric strength thereof is lowered, and the operating speed thereof is adversely affected.
Various efforts have been made to suppress the formation of a native oxide film. For example, there has been developed a load-lock semiconductor device fabrication apparatus for suppressing the formation of a native oxide film which would otherwise be deposited on the surface of a semiconductor substrate by oxygen trapped in a reaction chamber in a vertical low-pressure chemical vapor deposition (LPCVD) system. The load-lock semiconductor device fabrication apparatus has a load-lock chamber disposed between the reaction chamber and the exterior space for holding the inlet of the reaction chamber out of contact with the atmosphere. After the load-lock chamber is evacuated, an N.sub.2 atmosphere is introduced into the load-lock chamber. Quantitative data have been acquired which indicate the relationship between the densities of oxygen in the load-lock chamber and the reaction chamber and the thickness of a native oxide film. The effectiveness of the load-lock chamber is being widely recognized in the art.
In CVD systems, it is known that a trace amount of oxygen leaks from the exterior into a semiconductor device fabrication apparatus, e.g., from the exterior through an O-ring of a reaction chamber of quartz into the reaction chamber. The oxygen leakage causes a native oxide film to be formed on a semiconductor substrate, and also degrades the characteristics of a thin film deposited on the semiconductor substrate. Examples of degraded characteristics include many grain boundaries in a crystalline thin film and wrong crystalline directions.
It is important that semiconductor device fabrication apparatus be provided with load-lock chambers for mass-producing semiconductor devices fabricate semiconductor devices of stable and reproducible characteristics. However, there have not been proposed any significant means and systems for ensuring suring oxygen densities in load-lock and reaction chambers for stable and reproducible semiconductor device characteristics. Furthermore, no measures are presently taken to prevent a trace amount of oxygen from leaking into semiconductor device fabrication apparatus.
It is known to monitor a moisture in sputtering apparatus. Japanese laid-open patent publication No. 3-152924, for example, discloses a monitoring process for photo-excited vapor phase processing. However, it has not been known to monitor the density of oxygen in semiconductor device fabrication apparatus or the like.